None of the offered choices is correct.
The radical cannot be simplified. If rewritten, it must be written as something like
![x \sqrt[3]{ \frac{6}{x}}](https://tex.z-dn.net/?f=%20x%20%5Csqrt%5B3%5D%7B%20%5Cfrac%7B6%7D%7Bx%7D%7D%20)
or
Watch closely. I'll try to go slow.
Stop me if I go too fast, or if I do anything that you don't understand.
Ready ?
You said d = r t
Divide each side by ' t ' : d / t = r
Make a change of coordinates:


The Jacobian for this transformation is

and has a determinant of

Note that we need to use the Jacobian in the other direction; that is, we've computed

but we need the Jacobian determinant for the reverse transformation (from

to

. To do this, notice that

we need to take the reciprocal of the Jacobian above.
The integral then changes to
